The present invention relates to boxes for housing breathing masks used on board aircraft in order to accommodate such masks and comprising a door which is opened in such a way that each mask drops down at the disposal of a passenger and is supplied with a breathable gasp generally oxygen, in the event of depressurization.
For that, the boxes, each of which contains one or more masks, are normally kept closed by a catch. The catches of all the boxes are simultaneously disarmed in an emergency by supplying the mask supply pipes at a pressure higher than a determined threshold or by sending an electrical command to them.
The boxes have to be checked systematically on a regular basis. To do that, the box is opened manually by an operator who checks that a mask is stored and connected to the gas supply. During this operation, it often happens that a mask drops down and has to be put back, this being a tricky operation which takes time even though time is limited, especially when the operation is performed immediately before boarding.
It is an object of he present invention to provide boxes that make checking easier. To this end there is provided a box, the catch of which is associated with means which are rendered active by command, for example in response to a second pneumatic pressure (lower than a first pressure which disarms the catches when the catches are disarmed by applying a pneumatic pressure to the mask supply pipe), or via an electrical route, the said means then limiting the opening of the box to a partially opened position which prevents the mask or masks from dropping out when the catch is subsequently disarmed.
In an embodiment, said means consist of a plunger carried by the door, urged by return means into a position in which it is inactive and moved pneumatically into a position in which it cooperates with means carried by a housing of the box so as to limit the opening of the door when this plunger is moved by applying the second pressure. The door catch may be a simple magnet-ferromagnetic component assembly, the force of attraction of which is overcome by a push-rod when the latter is subjected to a breathable-gas pressure higher than a determined threshold.
The invention also has a second aspect, which can advantageously be used with the first, but which may be used independently thereof, takes account of the fact that the oxygen supply available on board an aircraft is limited. Following depressurization at high altitude, the masks drop down, the passengers are permanently supplied as soon as they open the individual supply tap to the mask by pulling on a cord to which the mask is attached, and the crew begins a descent then generally cuts off the oxygen supply once the aircraft has returned to about 10,000 feet or 3000 metres.
However, there is then the problem of maintaining an oxygen supply to those of the passengers who have not coped well with the depressurization or whose state of health so demands. The use of portable oxygen cylinders, which are bulky and heavy, provides only a rather unsatisfactory solution. Maintaining the supply by asking the cabin crew to shut off all the oxygen inlet taps of the masks other than those to which a supply needs to be maintained takes a great deal of time.
The invention also sets out to provide a masks box and an emergency oxygen supply device to address the above difficulties. To this end there is provided a box comprising, in addition to the tubes supplying the masks receiving the oxygen through a valve that opens automatically in the event that a supply pressure at least equal to a first value p1 is provided via an inlet pipe, an oxygen tapping equipped with a valve that opens automatically for as long as the pressure in the pipe exceeds a second value p3, less than p1 and possibly less than p2.
The pressures p1 and p3 may, for example, lie respectively between 3 and 4 bar and between 2 and 2.5 bar with respect to the pressure in the cabin. When the box is fitted with a catch allowing its opening to be limited, the pressure p3 will be chosen to be lower than p2. The following levels are, for example, possible:
p1: 350 kPa
p2: 240 kPa
p3: 200 kPa
The above characteristics, together with others, will become better apparent from reading the description which follows of some particular embodiments which are given by way of non-limiting examples. The description refers to the accompanying drawings.